JP3134522B2 - Dimming material and dimming element comprising the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dimming material comprising a liquid crystal and a polymer holding the liquid crystal, and a dimming element using the same. In particular, the present invention relates to a dimming element having a large change in light transmittance between when an electric field is applied and when no electric field is applied, and has excellent voltage sensitivity and the like, and a dimming material therefor.

[0002]

2. Description of the Related Art A dimming material composed of a liquid crystal and a polymer holding the liquid crystal scatters incident light due to a difference between a refractive index of the polymer and a refractive index of the liquid crystal when no electric field is applied.
When an electric field is applied, the liquid crystal is aligned in the direction of the electric field, so that the liquid crystal is in a transparent state.

This light modulating material is easy to increase in area and has advantages such as high durability as compared with ordinary liquid crystal display elements, and has recently been used for interior materials, large displays, automobiles and the like. Is expected for many uses.

Conventionally, as such a light control material, a liquid crystal in which a liquid crystal is microencapsulated with a polymer (Japanese Patent Publication No. 58-50).
1631), a liquid crystal dispersed in an epoxy resin in the form of fine droplets (Japanese Patent Publication No. 63-501512), and a liquid crystal held in a network polymer by photopolymerization using an acrylic oligomer (JP-A-63-27133). Etc. have been proposed.

[0005]

However, in the conventional light modulating material, the characteristics such as light transmittance, voltage sensitivity, film uniformity, durability, heat resistance, and temperature dependency are small in practice. Was not sufficiently satisfied.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a light modulating material and a light modulating element comprising the same, which solve the above-mentioned conventional problems, and in particular, have improved film uniformity, light transmittance, electric field sensitivity and heat resistance. .

[0007]

The light modulating material of claim 1 is:
A light modulating material comprising a liquid crystal and a polymer and controlling transmission and scattering of light depending on the presence or absence of an electric field, wherein the polymer is a dipentaerythritol compound represented by the following general formula (I): It is a polymer obtained by copolymerizing an acrylate compound represented by the formula (II).

[0008]

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[0009]

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According to a second aspect of the present invention, there is provided a light modulating device comprising a pair of substrates having electrodes on inner surfaces thereof, wherein at least one of the substrates has a transparent substrate. It is characterized by being performed.

That is, the present inventors have conducted intensive studies on polymers holding liquid crystals in order to solve the above-mentioned conventional problems. As a result, they have found that a specific dipentaerythritol compound and an acrylate compound are copolymerized. The present inventors have found that a dimming material using the obtained polymer exhibits good characteristics, and have reached the present invention.

Hereinafter, the present invention will be described in detail.

Among the monomers forming the polymer according to the present invention, in the dipentaerythritol compound represented by the general formula (I), R ^{1 to} R ⁶ in the general formula (I) are
The following substituents are shown, R represents a hydrogen atom or a methyl group,
n represents 0 or 1, and n of at least one of R ^{1 to} R ⁶ represents 1.

[0014]

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In the acrylate compound represented by the general formula (II), R ⁷ in the general formula (II) represents a hydrogen atom or a methyl group, and R ⁸ represents a methyl group, an ethyl group, a propyl group or a butyl group. A linear or branched alkyl group having 1 to 18 carbon atoms such as a pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, a decyl group, a dodecyl group, a tridecyl group, a pentadecyl group and a stearyl group; a cyclohexyl group Or a tetrahydrofurfuryl group; or-(R ⁹ O) _m -R ¹⁰ [R ⁹ is-(CH ₂ ) _k
- (k is an integer of _{2~11), - CH 2 CH 2} CH
_{(CH 3) -, - CH} 2 C (CH 3) 2 CH 2 -, - CH
_{(CH 3) CH 2 -,} - CH 2 CH (CH 3) -, - CH
_{(CH 3) - (CH 2} ) 3 -, - CH (CH 3) CH 2 CH 2
—, —CH ₂ C (C ₄ H ₉ ) ₂ CH ₂ —, etc.
1 represents a linear or branched alkylene group, and R ¹⁰ represents a carbon atom having 1 carbon atom such as a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, and an octyl group.
Represents a linear or branched alkyl group of from 8 to 8, and m is 1 to
Indicates an integer of 10. ].

As the acrylate compound represented by the general formula (II), the acrylate compound No. 1 having substituents R ⁷ and R ⁸ shown in Tables 1 and 2 below is used. 1 to 56 can be mentioned.

[0017]

[Table 1]

[0018]

[Table 2]

By photopolymerizing a polymerizable composition obtained by combining the compounds represented by the general formulas (I) and (II), the heat-resistant polymer according to the present invention can be obtained.
When this is used as a light control material, the light control material has excellent heat resistance and low temperature dependency. In the present invention, any of a nematic liquid crystal, a cholesteric liquid crystal, and a smectic liquid crystal can be used as the liquid crystal.

The nematic liquid crystal used in the present invention includes:
If it shows a nematic state in the operating temperature range, it can be selected in a considerably wide range. Further, a cholesteric state can be obtained by adding an optically rotatory substance described later to such a nematic liquid crystal. As examples of the nematic liquid crystal, No. 3 shown in Tables 3 to 5 below.
1 to 20 substances, or derivatives thereof.

[0021]

[Table 3]

[0022]

[Table 4]

[0023]

[Table 5]

In Tables 3 to 5, R 'represents an alkyl group or an alkoxy group, R represents an alkyl group, and X' represents an alkyl group, an alkoxy group, a nitro group, a nitro group, a cyano group, a trifluoromethyl group, and a trifluoro group. Represents a methoxy group or a halogen atom. The hydrogen of the benzene ring in Tables 3 to 5 is
Further, it may be substituted with a fluorine atom.

The liquid crystal used in the present invention may be any of the liquid crystals shown in Tables 3 to 5 or a mixture containing them. For example, "ZLI-1132" and "Z
Liquid crystal or British Dru sold under the trade name "LI-1840" or "ZLI-1565"
g “E-7”, “E-8”, “E-
37 "," E-44 "," E-46 "or" BL00 "
Liquid crystal or the like sold under the trade names of “1” to “BL020” can be used.

A cholesteric state can be obtained by adding the following optically active substance to such a nematic liquid crystal.

In this case, the optically active substance used in the liquid crystal composition includes a chiral nematic compound such as 2
Compounds in which optically active groups such as -methylbutyl group, 3-methylbutoxy group, 3-methylpentyl group, 3-methylpentoxy group, 4-methylhexyl group, and 4-methylhexoxy group are introduced into nematic liquid crystal. Also, alcohol derivatives such as 1-menthol and d-borneol shown in JP-A-51-45546, d-camphor,
Ketone derivatives such as -methylcyclohexane, carboxylic acid derivatives such as d-citronellic acid and 1-camphoric acid, d-
Optically active substances such as aldehyde derivatives such as citronellal, alkene derivatives such as d-linonene, and other amines, amides, and nitrile derivatives can also be used.

The smectic liquid crystal used in the present invention includes a smectic A liquid crystal and a smectic chiral C liquid crystal.

The method for producing the light modulating material of the present invention is not particularly limited. For example, a polymerizable composition comprising the liquid crystal and the monomers represented by the general formulas (I) and (II) The product and the photopolymerization initiator are mixed, optionally heated to form a uniform solution, and exposed to a predetermined amount of ultraviolet light or an electron beam.
As a result, the compound represented by the general formula (I) and the compound represented by the general formula (I
The compound represented by I) is copolymerized, and the copolymer and the liquid crystal are in a phase-separated state, whereby a polymer-preserving liquid crystal light modulating material can be obtained.

At this time, the ratio of the compound represented by the general formula (I) to the compound represented by the general formula (II) is 10/1.
To 1/10 (compound (I) / compound (II); weight ratio), preferably 1/1 to 1/10. The compound represented by the general formula (I) and the compound represented by the general formula (II) may be used as a mixture of two or more kinds.

Examples of the photopolymerization initiator include 2,2-dimethoxy-2-phenylacetophenone and 2-hydroxy-2.
-Methyl-1-phenylpropan-1-one and the like.

The ratio of the liquid crystal in the homogeneous solution is as follows:
The content is preferably 40 to 90% by weight, particularly 65 to 85% by weight.
% By weight.

In the above reaction system, if necessary, a surfactant, a light stabilizer, a dichroic dye, a non-dichroic dye, a chain transfer agent, a photosensitizer, a crosslinking agent and the like are used in combination. be able to.

On the other hand, the electrodes of the light control device of the present invention include:
Generally, a transparent electrode such as ITO (indium tin oxide) is used, and a transparent substrate such as a plastic plate such as glass or polyester is used as the electrode substrate.

In manufacturing the light modulating device of the present invention, it is preferable to include a spacer in the light modulating material in order to increase the area or obtain a more uniform film thickness. The spacer is not particularly limited, but a glass or a spherical or rod-shaped spacer made of a polymer such as polyvinylbenzene or polymethyl methacrylate can be used. As a method of using such a spacer, there is a method of applying the polymerizable composition after spraying on the substrate, or a method of uniformly dispersing the polymerizable composition in the polymerizable composition and introducing the spacer between the substrates.

When a pair of transparent electrode substrates is used as the substrate, the dimming element of the present invention can be used as a transmissive dimming element, one of which uses a transparent and the other an opaque electrode substrate. In that case, a reflective layer can be placed after the opaque electrode substrate to be used as a reflective dimming device.

The light modulating element of the present invention comprises, for example, sandwiching a uniform solution containing the above-mentioned liquid crystal, polymerizable composition and photopolymerization initiator, and, if necessary, various additives, between substrates having the electrodes, It can be easily produced by polymerizing the polymerizable composition upon exposure to light. Alternatively, it can also be produced by applying the uniform solution on a substrate, polymerizing the solution, and then laminating the substrates.

[0038]

A dipentaerythritol compound represented by the above general formula (I) is used as a polymer holding a liquid crystal.
By using a polymer obtained by copolymerizing with the acrylate compound represented by the general formula (II), a light modulating material excellent in various properties is provided.

By using such a light control material,
Characteristics such as film uniformity, light transmittance, electric field sensitivity, and heat resistance of the light control device are greatly improved.

[0040]

Next, the present invention will be described in more detail with reference to examples and comparative examples.
The present invention is not limited to the following embodiments.

Example 1 Dipentaerythritol compound Ia (in the general formula (I), R ^{1 to} R ³ are —CO—CH ₂ CH ₂ CH ₂ CH
₂ CH ₂ O—CO—CH ＝ CH ₂ , R ^{4 to} R ⁶ are —CO
-CH = CH ₂₎ 0.1g, of Table 1 No. 7, an acrylate compound IIa (in the general formula (II), R
⁷ is H, R ⁸ is _{-CH 2 CH (C 2 H 5} ) C 4 H 9)
0.2 g, 2,2-dimethoxy-2- as a polymerization initiator
A uniform solution was obtained by mixing 0.006 g of phenylacetophenone and 0.7 g of E-8 (manufactured by BDH) as a liquid crystal, and 0.015 g of a plastic (divinylbenzene copolymer) spacer having a diameter of 10 μm in this solution. Was added, and the mixture was inserted between a plastic substrate with ITO (polyethylene terephthalate) having a size of 6 cm × 9 cm, and exposed with an ultraviolet irradiation device to obtain a uniform light control element without cracks or the like. Note that the applied energy is equivalent to 400 mJ.

An AC electric field (60 Hz,
Sine wave) was applied, and the voltage dependence of the parallel light transmittance change was measured by a digital turbidimeter (Nippon Denshoku Industries Co., Ltd .; NDH-20D type).
It was confirmed that both the voltage sensitivity and the transmittance change exhibited good characteristics.

T ₀ = 10.6% T ₁₀₀ = 81.3% V ₁₀ = 17V V ₉₀ = 38V Transmittance difference = 70.7% where T ₀ : light transmittance at 0 applied voltage, T ₁₀₀ : Light transmittance when the applied voltage is increased and the light transmittance becomes almost constant; V ₁₀ : applied voltage at which the transmittance becomes 10% when T ₀ is 0% and T ₁₀₀ is 100%; V ₉₀ : applied voltage at which the left light transmittance becomes 90%, and the difference in transmittance is T ₁₀₀ -T ₀ .

Example 2 In place of the acrylate compound IIa,
Except for using the acrylate compound IIb shown in No. 35 (in the general formula (II), R ⁷ is H and R ⁸ is a cyclohexyl group), a crack-free uniform light control device was obtained in the same manner as in Example 1. Obtained. The results of measurement of this light control device in the same manner as in Example 1 are as follows, and it was confirmed that both the voltage sensitivity and the change in transmittance exhibited good characteristics. T ₀ = 10.2% T ₁₀₀ = 81.2% V ₁₀ = 15V V ₉₀ = 30V Transmittance difference = 71.0% Example 3 Instead of the acrylate compound IIa,
Except for using an acrylate compound IIc (in the general formula (II), R ⁷ is a methyl group and R ⁸ is a tetrahydrofurfuryl group) shown in 34, the same as in Example 1
A uniform light control element without cracks was obtained. The results of measurement of this light control device in the same manner as in Example 1 are as follows, and it was confirmed that both the voltage sensitivity and the change in transmittance exhibited good characteristics.

T ₀ = 10.7% T ₁₀₀ = 79.5% V ₁₀ = 16V V ₉₀ = 32V Transmittance difference = 68.8% Example 4 Instead of the acrylate compound IIa,
Except for using the acrylate compound IId shown in No. 3 (in the general formula (II), R ⁷ is H and R ⁸ is —C ₄ H ₉ (n)), cracks and the like No uniform light control element was obtained. The measurement result of this light control element in the same manner as in Example 1 was as follows, and it was confirmed that the light control element exhibited good transmittance change characteristics.

T ₀ = 10.2% T ₁₀₀ = 81.0% Transmittance difference = 70.8% Example 5 Instead of dipentaerythritol compound Ia, dipentaerythritol compound Ib (general formula (I) In the formula, R ^{1 to} R ⁶ represent —CO—CH ₂ CH ₂ CH ₂ CH ₂ C
Except for using H ₂ O—CO—CH 用 い CH ₂ ), a uniform light control device without cracks was obtained in exactly the same manner as in Example 4. The measurement result of this light control element in the same manner as in Example 1 was as follows, and it was confirmed that the light control element exhibited good transmittance change characteristics.

T ₀ = 10.8% T ₁₀₀ = 75.9% Transmittance difference = 65.1% Example 6 Instead of the acrylate compound IIa,
23 is an acrylate compound IIe (in the general formula (II), R ⁷ is H and R ⁸ is — (CH ₂ CH ₂ O) ₂ CH
Except that ₃ ) was used, exactly the same as in Example 1
A uniform light control element without cracks was obtained. The results of measurement of this light control device in exactly the same manner as in Example 1 are as follows, and it was confirmed that the device exhibited good transmittance change characteristics. T ₀ = 10.1% T ₁₀₀ = 79.8% Transmittance difference = 69.7% Comparative Example 1 In Example 1, dipentaerythritol compound I
In the same manner as above except that 0.3 g of a was used and that the acrylate compound IIa was not used, a uniform light control device without cracks or the like was obtained. The measurement result of this light control device in the same manner as in Example 1 was as follows, and it was confirmed that the transmittance change was small and the light control device was not preferable.

T ₀ = 31.9% T ₁₀₀ = 43.8% Transmittance difference = 11.9% Comparative Example 2 In Example 5, dipentaerythritol compound I
In the same manner except that 0.3 g of b was used and the acrylate-based compound IId was not used, a uniform light control device without a crack or the like was obtained. The measurement result of this light control device in the same manner as in Example 1 was as follows, and it was confirmed that the transmittance change was small and the light control device was not preferable.

T ₀ = 24.2% T ₁₀₀ = 31.0% Transmittance difference = 6.8% Comparative Example 3 In Example 4, 0.3% of the acrylate compound IId was used.
g, and no dipentaerythritol compound Ia was used, to produce a light control device in the same manner. However, no phase separation occurred, and a uniform light control film was not obtained.

[0050]

As described in detail above, the light modulating material of the present invention has good film uniformity, and the light modulating element of the present invention using the light modulating material can be used when the electric field is applied and when no electric field is applied. It has excellent transmittance difference, voltage sensitivity, repetitive response, and heat resistance, and is extremely useful as a high-performance light control element used for a display device, a light control window, and the like.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C09K 19/54 CA (STN) REGISTRY (STN)

Claims (2)

(57) [Claims] 1. A light modulating material comprising a liquid crystal and a polymer and controlling transmission and scattering of light by the presence or absence of an electric field, wherein the polymer is a dipentaerythritol-based compound represented by the following general formula (I): A light modulating material, which is a polymer obtained by copolymerizing a compound and an acrylate compound represented by the following general formula (II). Embedded image Embedded image 2. A pair of substrates having electrodes on the inner surface, wherein at least one of the substrates is formed by sandwiching the light control material according to claim 1 between transparent substrates. Light control element.